The present invention relates to an osteosynthesis device, particularly for spinal support or correction, that can be used in particular for internal implantation.
For spinal support or correction, a device comprising one or more support bars positioned along the spinal column is used, and fixed to certain vertebrae by implants. Said implants are fixed at one end to the bars and at the other end to the vertebrae by bone anchorage means, composed of a hook supported by a vertebra or of a threaded part screwed inside the vertebra itself, for example at the pedicle.
In such devices, it is known to use bars inserted into the body of the implant via an opening, either simply through the implant or in the form of a channel opening onto a side, said channel possibly opening onto the side or rear (on the top of the implant).
In the case of a closed type implant, the insertion of the bar must most frequently be carried out after the fixation of the implants, which requires the delicate operation of deforming the bar as it is inserted into the different implants.
In the case of an implant with a side or rear opening, the bar-implant fixation may be obtained by means of an intermediate part referred to as a clamp. Said clamp is formed from a ring which is inserted around the bar and fixed to it by a clamping screw, said clamp in turn being inserted into the opening of the implant longitudinally along the axis of the bar. Once the clamp is inserted longitudinally in the implant, as in patent FR 2 545 350, the clamping is obtained by a conical shank and secured by an additional part referred to as a safety lock. Failing a safety lock, as in patent EP 0 392 927, the clamping is secured by two additional screws clamped onto the bar via the clamp and the body of the implant.
Another possibility consists of inserting the bar directly into an implant with a rear open channel, as in patent FR 2 680 461, and clamping this bar with a threaded plug securing the bar by means of a curved blade to provide a satisfactory contact surface.
In both cases, this assembly of several parts is intended to ensure the reliability of the clamping, but represents a complexity and size liable to render implantation delicate, particularly at the junction of the lumbar and sacral regions where only a small amount of space is available due to anatomical conditions. The presence of small parts to assemble during the operation involves the disadvantage of more delicate manipulations and the risk of said small parts being disseminated in the operative field.